The present invention relates generally to capacitive keys for use in keyboards, and particularly to space bars for use in low profile keyboards. The arrangement is such that a self-contained module is provided which may accommodate a 1 by 3 up to a 1 by 9 space bar, which module after assembly may be subsequently inserted into the keyboard, as required.
This invention relates also, to co-pending U.S. application Ser. No. 349,349 filed Feb. 16, 1982 and entitled Low Profile Keyboard Switch, which application is incorporated herein, by reference, in its entirety. In that application, a self-contained key switch module is disclosed which provides an extraordinarily low profile keyboard for capacitive keys with the keyboard switch having a substantially reduced overall height of 0.75 inches (19.05 mm) while still maintaining a length of travel of 0.15 inches (3.81 mm). The construction taught in that application eliminates the need for any housing for the switch assembly of the key switch unit by providing a combination assembly supported directly on the printed circuit board. The parts of the assembly are snap-fitted together, eliminating the need for hardware such as screws or nuts for connecting the parts.
This invention is an improvement over the assembly taught therein for use when space bars are required. The module of the invention here is a space bar unit which may be snap-fitted into a capacitive keyboard in the same manner as the single unit assembly of that co-pending application Ser. No. 349,349.
The space bar construction of the invention here provides a leveling system for space bars so that both ends of the space bar go down exactly at the same time. This is achieved by utilizing a torsion spring for the leveling wire which extends between each end of the space bar. With such a construction, pressure is always applied to the leveling wire, which eliminates noise in a loosely mounted wire as used previously.
One of the problems involved with prior art arrangements is the fact that the leveling wire extending between two independent plungers for manipulating the space bar must have mechanical tolerance between each of the plungers. This loose fit between the plungers and the leveling wire allows the leveling wire to rattle creating an objectionable noise. The new arrangement herein minimizes noise since the leveling wire is always preloaded against the plungers by the torsion spring.
With the foregoing and additional objects in view, this invention will now be described in more detail, and other objects and advantages thereof will be apparent from the following description, the accompanying drawings and the appended claims.